Several major Cardiac Rhythm Management (CRM) companies have developed special pacemakers “IPGs” that allow for the delivery of resynchronization therapy. This technology uses atrial, synchronized, biventricular pacing and requires placement of a lead in or on the right atrium as well as the right and left ventricles. Placement of a lead inside the left ventricle has not been clinically feasible to date due to dislodgement and the risk of embolism formation potentially leading to a stroke. Placement outside the left ventricle now often includes placing a lead in a convenient location instead of the most efficacious location.
To answer the challenge of placing the left ventricle (LV) lead, considerable effort has gone into the development of special leads and delivery systems for placing the LV lead in a coronary vein. These leads are often referred to as coronary sinus (CS) leads, since the lead passes through the CS. CS leads have been challenging for the electrophysiologist to place and often require considerably more time and increased fluoroscopy exposure than traditional endovascular right side leads. Following implantation, the CS lead may dislodge in 10+% of patients leading to less than desirable performance. At least 10% of the target patients are not candidates for CS leads due to the anatomical structure of their coronary veins.
An alternative to CS leads is the use of epicardial or myocardial leads. Traditionally, these leads have been placed during open chest surgical procedures (sternotomy) or through a less traumatic subxiphiod or subcostal approach to the apex of the heart. The invasiveness of a full sternotomy would not be well tolerated by the CHF patients.
It is generally believed that the target location on the heart for resynchronization therapy is the lateral side of LV 2-3 cm apical of obtuse marginal and circumflex artery junction. Optimization of the target site may be achieved by ECG mapping of the heart to determine the location on the left ventricle that has the latest activation. To reach the target location through MI techniques, endoscopic ports and special endoscopic instruments may be employed. During a minimally invasive procedure it may be desirable to pass the device through a port. The port ID and length limit the amount of curvature that can preexist in some implant tools.
It is desirable for a lead to be implanted with the center axis of the helical electrode normal to the surface of the heart.
Some current epicardial leads and methods require rather large incisions to place the leads. The Fast Tac Flex implant tool (available from Enpath Medical, Minneapolis Minn.) reduces the invasiveness of the procedure, but may be more difficult to use on the posterior side of the heart.
What would be desirable is a device which provides improved minimally invasive access for lead placement on the heart. In particular, what would be advantageous is a device which provides minimally invasive placement of an epicardial lead on the posterior side of the heart. What would especially be advantageous are devices and methods providing visualization and electronic mapping to find the most efficacious lead electrode position to provide optimal patient outcomes.